Projections of leaf turgor loss point shifts under future climate change scenarios

Abstract Predicting the consequences of climate change is of utmost importance to mitigate impacts on vulnerable ecosystems; plant hydraulic traits are particularly useful proxies for predicting functional disruptions potentially occurring in the near future. This study assessed the current and future regional patterns of leaf water potential at turgor loss point (Ψtlp) by measuring and projecting the Ψtlp of 166 vascular plant species (159 angiosperms and 7 gymnosperms) across a large climatic range spanning from alpine to Mediterranean areas in NE Italy. For angiosperms, random forest models predicted a consistent shift toward more negative values in low‐elevation areas, whereas for gymnosperms the pattern was more variable, particularly in the alpine sector (i.e., Alps and Prealps). Simulations were also developed to evaluate the number of threatened species under two Ψtlp plasticity scenarios (low vs. high plasticity), and it was found that in the worst‐case scenario approximately 72% of the angiosperm species and 68% of gymnosperms within a location were at risk to exceed their physiological plasticity. The different responses to climate change by specific clades might produce reassembly in natural communities, undermining the resilience of natural ecosystems to climate change.

. The increase in drought frequency and intensity is associated with declining forest productivity (Poorter et al., 2017) and pulses of tree mortality, mainly caused by hydraulic failure (Hammond et al., 2019;Senf et al., 2020), even in biomes which are less prone to these events (i.e., temperate and tropical humid forests; Phillips et al., 2009;Powers et al., 2020). On this basis, anticipating climate change impacts on plant communities and improving our understanding of their potential vulnerabilities among different clades needs to improve (Choat et al., 2012). This holds true particularly for plant communities growing in terrestrial biomes highly vulnerable to these changes, such as alpine forests and Mediterranean vegetation (Giorgi, 2006;Seddon et al., 2016).
During drought events, soil moisture declines in response to low precipitation coupled with high evaporative demand. One of the first responses of plants to water shortage is stomatal closure, which limits water loss, maintains adequate cell hydration, and prevents water potential (Ψ) from dropping to values that induce cell turgor loss or xylem embolism, which may ultimately lead to plant damage and death (Choat et al., 2018;Zhu et al., 2018). Leaf water potential at turgor loss point (hereafter turgor loss point, Ψ tlp ) is a measure of the capability of plants to maintain cell turgor under water stress, and is related to stomatal kinetics and water-use efficiency (Brodribb et al., 2003;Petruzzellis et al., 2021). This is strongly controlled by phylogeny and growth forms because woody angiosperms have better optimized water-use efficiency with respect to older lineages and herbaceous angiosperms (Brodribb et al., 2003), even though recent evidence has challenged the view of woody species being more drought resistant than herbaceous ones (Lens et al., 2016). Ψ tlp is a good proxy of species-specific drought tolerance McGregor et al., 2021;Zhu et al., 2018), and lower Ψ tlp is based on osmoregulation, namely increased cell solute content that lowers the osmotic potential at full turgor (π 0 ) . Lower Ψ tlp allows plants to better tolerate water shortage while maintaining positive carbon balance and preventing cellular damage (Blackman et al., 2010;Brodribb et al., 2003), thus ensuring better chances to survive under intense and/or prolonged drought (Nardini et al., 2013). The intimate relation between Ψ tlp and drought tolerance has been reported for several species across different biomes (Bartlett et al., 2014;Zhu et al., 2018) and water availability (Medeiros et al., 2019;Petruzzellis et al., 2021;Tordoni, Petruzzellis, et al., 2020). Turgor loss point is typically lower in arid and saline habitats such as saltmarshes (Rosas et al., 2019;Tordoni et al., 2019), although recent research detected a higher survival in herbaceous species characterized by higher Ψ tlp in temperate grasslands (Sun et al., 2020). Similar to drought tolerance, plants can resist frost damage by lowering π o (Beck et al., 2007;Charrier et al., 2021 and references therein), because ice formation in the apoplast typically leads to cellular dehydration.
Plant water status influences photosynthesis and ecosystem productivity, which in turn is linked to carbon and hydrological cycles (Adams et al., 2017;Brodribb, 2009;Choat et al., 2018). Thus, the inclusion of such mechanistic traits when modelling vegetation responses to climate is crucial to capture reliable trends and improve projections of climate change impacts . In addition, given their high degree of conservatism within species, these parameters are very useful for trait-based modelling (Fuchs et al., 2021). Recent methodological advancements (Bartlett, Scoffoni, Ardy, et al., 2012;Griffin-Nolan et al., 2019;Petruzzellis et al., 2019) allow faster measurements of Ψ tlp compared with traditional methods (e.g., pressure-volume curves), thus enabling its quantification in larger species pools.
To the best of our knowledge, no previous study has provided a spatialization of Ψ tlp at a regional scale. Most importantly, the possible use of Ψ tlp to model vegetation shifts under climate change projections have not been previously tested. This study reports measurements of Ψ tlp for 166 vascular plants (159 angiosperms and 7 gymnosperms). The spatial distribution of this trait was assessed in a grid covering a large climatic gradient spanning from Mediterranean to alpine areas in NE Italy. Additionally, the possible future spatial distribution of Ψ tlp in two climate scenarios was modeled under low and high concentration of greenhouse gases (representative concentration pathway, RCP 2.6 and RCP 8.5, respectively). Specifically, this study aimed to (a) assess the spatial patterns of Ψ tlp , (b) identify the main climatic determinants of Ψ tlp variation, and (c) predict future changes in Ψ tlp distribution based on climatic projections up to 2100.
It was hypothesized that a different spatial pattern of Ψ tlp would occur for angiosperms and gymnosperms, as well as more negative values of Ψ tlp in areas characterized by high frequency of drought and/or frost events (i.e., mountain valleys, coastal areas).

| Study area
The study was carried out in Friuli Venezia Giulia region (FVG,geographical limits between 45°35′ N and 46°39′ N,and 12°20′ E and 13°07′ E). The territory is predominantly mountainous (42.5% of the total area) spanning from 0 to 2780 m above sea level (a.s.l.) and is dominated by Carnic and Julian Alps in the northern part. The southern part is characterized by wide plains degrading toward the Grado-Marano Lagoon and the Adriatic Sea. The South-eastern part is dominated by classical Karst ( Figure S1). Approximately 90% of the region has a temperate climate, the remaining 10% being as- Mean annual temperature of the alpine sector is approximately 9°C, with minimum temperatures reaching −25°C, while rainfall is abundant and ranges from 1500 to 3000 mm/year in the Julian Alps. Due to such environmental and climatic heterogeneity, FVG hosts a remarkable variety of habitats and is an important hotspot of endemic plant diversity (Tordoni, Casolo, et al., 2020). Vegetation type in the study area ranges from alpine grasslands and tundra formations to coniferous forests on the summits of the alpine sector, replaced by mixed-forest or beechwoods and broadleaved forests at lower elevations. The lowlands are intensively exploited for crop growth, even though some seminatural patches characterized by grasslands, alkaline fens, and marshes do still occur in the area. The southern coastline and the lagoon are dominated by halophyte and psammophyte communities, while the vegetation of the typical Karst is mainly composed by xero-thermophilus bushes and small trees, intermixed with large patches of Pinus nigra plantations. of latitude × 5′ of longitude (ca. 5.5 × 6.5 km), following the Central European grid for floristic surveys (Ehrendorfer & Harmann, 1965).

| Species distribution
However, because some OGUs on the borders have incomplete data, they were excluded from the data set, thus maintaining 264 OGUs for analysis. Species' names were standardized according to the updated checklist of Italian vascular flora (Bartolucci et al., 2018).

| Climatic data
A set of climatic predictors was obtained from climate simulations performed by the International Center of Theoretical Physics (ICTP) within the EURO-CORDEX (https://www.euro-cordex.net) and MED-CORDEX (https://www.medco rdex.eu) projects, aimed at providing improved regional climate change projections for Europe.
Data are available at daily temporal resolution, with spatial resolution of 0.10° (ca. 11 km) and can be downloaded from the website of the environmental protection regional agency (https://www.osmer. fvg.it). The data set consists of 16 climatic parameters (including precipitation, surface temperature, and evaporation), encompassing the historical period of 1970-2005, along with simulations for the period 2006-2100 under three RCP scenarios (RCP 2.6, RCP 4.5, and RCP 8.5). For this study, only RCP2.6 and RCP 8.5 were considered. From these climatic data, a set of six biologically relevant variables were derived (sensu https://www.world clim.org) to quantify both average climate conditions and climatic limits, particularly in relation to drought or frost events. The selected variables were: 95th percentiles of average temperature (BIO1.95, °C), temperature seasonality (BIO4, °C), annual consecutive frost days where temperature was ≤0°C (CFD.ann, n° days), annual consecutive dry days where precipitation was <1 mm (CDD.ann, n° days), 5th percentiles of cumulate annual precipitation (BIO12.5, mm), and precipitation seasonality (BIO15, %). Data were extracted and processed using "ncdf4" (Pierce, 2019) and "raster" (Hijmans, 2021) R packages. For each Operative Geographic Unit, the weighted average value of the climatic variable within each grid cell was extracted based on occupancy within the OGU. Finally, the average value for the historical period was calculated, and for future projections the average value for the period 2080-2100 was computed.

| Sampling design and turgor loss point measurement
In total, samples from 166 vascular plant species were collected, representing the most abundant taxa in the regional flora (see Table S1 for the species list). Specifically, 159 angiosperms were sampled which represent approximately 8% of the angiosperms in the region (10% for herbaceous species and 20% for woody species, respectively), and 7 gymnosperms encompassing 39% of all gymnosperm species occurring in the study area. Measurements were performed on three individuals for both herbaceous (one replicate per individual) and woody species (three replicates per individual). Measurements for 124 species were obtained in a previous sampling campaign (see Petruzzellis et al., 2021), while the remaining 73 species were selected following a double-criterion approach, based on their frequency in the study area and on their representativeness in the regional habitats (ISPRA, 2009), according to the European Habitats Directive (92/43/EEC). In detail, FVG was divided in five areas reflecting the main orographic units

| Spatial patterns of turgor loss point
Considering that a simple average of Ψ tlp values could not provide a reliable estimate of the average species' drought resistance in each grid due to differences in species abundance and representativeness, a four-step procedure was applied to estimate the weighed value of Ψ tlp in each OGU. The following steps were ap-  3) The species not present in the grid were filtered out, and the Ψ tlp associated with each habitat (Ψ tlp_hab ) was computed as a weighted average, using the species' importance as a weight.
(4) Finally, following an approach similar to community-weighted means (Lavorel et al., 2008), Ψ tlp_hab was multiplied by the relative abundance of the habitat to obtain the average value of Ψ tlp over the whole habitat within a grid cell. To effectively remove effects due to phylogeny and growth form, the whole species pool was divided into four subsets (gymnosperms, angiosperms, herbaceous, and woody angiosperms), and for each group Ψ tlp was calculated following the procedure described above.

| Statistical analysis
First, one-way ANOVA was used to test for significant differences in Ψ tlp among different habitats, ensuring that the model's assumptions were met. Post-hoc multiple comparisons were performed using Tukey's "Honest Significant Difference" method available in "agricolae" (de Mendiburu, 2021) R package. Random forests (RFs) was used to model the spatial patterns of Ψ tlp and the main climatic determinants, as this class of model proved to deal with overfitting and multicollinearity, performing well also in the presence of non-linear relationships or complex interactions (Cutler et al., 2007;Mansfield et al., 2020). Four RFs were trained for each model using Ψ tlp as a function of climatic variables using "mlr3" (Lang et al., 2019) and "mlr3spatiotempcv" (Schratz & Becker, 2021) R packages. The following parametrization was used to start building the decision trees: sample fraction = 0.6, number of variables to possibly split at each node (mtry) = 1, number of trees (ntree) = 500, minimal size of the node (min.node.size) = 1, which was later tuned using the "paradox" (Lang et al., 2021) R package. Before computing the models, all the climatic predictors were centered and scaled to unit variance.
Variable importance was assessed by estimating the average change in root mean square error (RMSE) after variable permutations (N = 500) using "DALEX" R package (Biecek, 2018). This method assumes a worsening of the model's performance (i.e., an increase in RMSE) when permuting an important variable caused by a loss in explanatory ability (see Fisher et al., 2019 for more technical details).

| Threatened species based on plasticity simulations
To evaluate the number of species potentially threatened by climate change, for each grid cell the predicted Ψ tlp was first assessed by averaging the predictions deriving from the RFs. By assuming that the measured Ψ tlp of each species represents the median value of its seasonal plasticity, two simulations were performed (high and low plasticity, respectively) where the species were deemed capable to adjust their Ψ tlp by 0.44 and 0.22 MPa (Bartlett et al., 2014). Finally, the relative number of species in each OGU (expressed as %) whose plasticity range was lower, higher, or does not include the predicted Ψ tlp of the OGU was estimated. This simulation was performed for pooled angiosperms and gymnosperms, considering only the highemission scenario (RCP 8.5).

| RE SULTS
Different habitats were characterized by a significant degree of variation in the observed Ψ tlp (one-way ANOVA test F [13,262] = 7.55, p < .001). Notably, saltmarshes and Mediterranean evergreen oak woodlands hosted species with lower Ψ tlp compared with other habitats. Crops, mesophilous grasslands and freshwater habitats generally hosted species less resistant to drought (higher Ψ tlp ) ( Figure S2).
A clear and consistent spatial pattern in Ψ tlp was observed between angiosperms and gymnosperms (Figure 1), despite a substantial difference in the magnitude of variation, exceeding 1 MPa in some locations. Gymnosperms (Figure 1a) showed more negative values in the Prealps and in some portions of the Karst area (see Figure S1 for a detailed overview of the main orographic units in the region).
Consistently, angiosperms (Figure 1b) displayed more negative values mainly in the Prealps and Alps and in the south-eastern area (i.e., the lagoon and the Karst, respectively). Within angiosperms, herbaceous species showed a pattern of Ψ tlp variation consistent with that observed for the whole pool of angiosperms, with more negative values in the alpine sector and the Karst. Herbaceous species showed larger variation of Ψ tlp than woody angiosperms, whose drought resistance was evenly distributed in the region (Figure 1d).

| Drivers of turgor loss point variation and future shift projections
All RFs showed good performance in predicting the Ψ tlp with an average R 2 ≈ 0.49 and an RMSE ≈ 0.11 across the different models (Table S2). For sake of readability, only one model is reported in F I G U R E 1 Spatial patterns of Ψ tlp (MPa) in (a) gymnosperms, (b) angiosperms, (c) herbaceous angiosperms, and (d) woody angiosperms. Cell size is 3′ × 5′ (lat/long; ca. 5.5 × 6.5 km). Cells with no data are represented in light gray.
the main text, which best depicts the overall trends in the data set ( Figure 2), but information related to the other models are available in Figures S3 and S4.
For all groups, except for woody angiosperms, the most important variables were temperatures (BIO1.95) and consecutive frost days (CFD.ann), while precipitation seasonality (BIO15) was important only for woody angiosperms (Figure 2d). In the other climatic models, consecutive dry days (CDD.ann) and the 5th percentiles of cumulate annual precipitation (BIO12.5) also emerged as important predictors of the spatial variation of Ψ tlp ( Figure S3). Notably, all the models converged in predicting consistent shifts of Ψ tlp with relatively low variation among them ( Figures S5 and S6), even though slight differences were detected based on the group and the model considered (Figure 3, Figures S7 and S8). All the groups showed consistent trends toward more negative values of ΔΨ tlp particularly in the lowlands, although herbaceous angiosperms showed an increasing trend of ΔΨ tlp in the southern part of the study area which encompassed the lagoon (Figure 3c). Gymnosperms displayed a negative trend in the lowland areas, while in the Alps and Prealps the pattern was more variable (Figure 3d), likely due to the larger environmental heterogeneity in these grid cells.
The simulations suggested that in the low plasticity scenario, a mean value of 72 ± 8% (mean ± SD) of angiosperm species (49 ± 7% in the high plasticity scenario) within the study area resulted in potential threat by climate change at a local scale. For gymnosperms, 69 ± 28% (19 ± 23% in the high plasticity scenario) of the species in the data set ( Figure 4) were at risk. Also detected was a clear spatial pattern of variation, with decreasing Ψ tlp in the lowlands, but increasing Ψ tlp in the mountain areas, with a slight increase in the relative number of threatened species in the low plasticity scenario ( Figure S9). In contrast, gymnosperms were mainly threatened by a potential increase in Ψ tlp values in both simulations, particularly where the one simulating a lower plasticity displayed a slight trend consistent with the orography of the study area ( Figure S10).

| Projected shifts of Ψ tlp in relation to climate change
Ψ tlp has recently emerged as a good predictor of plant distribution in response to climatic conditions (Fuchs et al., 2021;Rosas et al., 2019), as it is mechanistically related to drought resistance Maréchaux et al., 2018). Specifically, species living in drier environments generally have lower Ψ tlp than species living in areas where water is not a limiting factor (Binks et al., 2016;Fuchs et al., 2021). Ψ tlp is also effective in detecting plant performance under drought conditions or in response to climate change McGregor et al., 2021), whereby species capable of major osmotic adjustments can better withstand water shortage (Binks et al., 2016;Fuchs et al., 2021). In this study, Ψ tlp spatial variation was mainly related to differences in temperaturerelated variables, precipitation, and duration of dry spells (Figure 2), which could all be considered as proxies of environmental water availability. Specifically, lower Ψ tlp was found in grid cells with higher temperatures and higher CFD, as well as in those with lower precipitation and higher CDD, confirming previous conclusions on Ψ tlpenvironment relationships Bourne et al., 2017;Flo et al., 2021;Rosas et al., 2019). The major physiological determinant of Ψ tlp is the cell osmotic potential, which reflects intracellular solute concentration. As a result, species able to decrease their π 0 under drought can thus lower their Ψ tlp  and maintain stomatal aperture, photosynthetic gas exchange and growth under water shortage (Blum, 2017;Merchant et al., 2007). In this light, the results confirm that osmoregulation is a key mechanism to cope with both high and low temperature extremes. For example, frost stress can induce water limitation, with possible effects on similar physiological processes affected by drought, such as membrane permeability and stability, water content, and risk of plasmolysis (Charrier, 2021). In this light, the accumulation of solutes (i.e., osmoregulation) is essential to (1) decrease the freezing point in both living cells and apoplast Lintunen et al., 2018) at low temperature extremes and (2) maintain cell hydration by minimizing water loss at high temperature extremes (Chen & Jiang, 2010). Moreover, water stress is exacerbated by the combination of limited water availability and high temperatures in dry and hot areas (such as the coastal and Karst orographic units in the study region, Figure S1), as high temperature increases the evaporative demand of the atmosphere (i.e., higher vapor pressure deficit, VPD), thus increasing water loss through transpiration (Bartlett & Sinclair, 2021). In these areas, reduced water supply and high VPD could cause a drop in xylem pressure below critical thresholds causing embolism formation in xylem conduits, ultimately leading to extreme failure of the water transport system (McDowell et al., 2022). To cope with these conditions, plants can shift physiologically critical thresholds of water status, by decreasing Ψ tlp and/or Ψ 50 (i.e., water potential inducing 50% loss of hydraulic conductivity) (McDowell et al., 2022). Alternatively, plants can avoid the reduction of xylem pressure by increasing water transport capacity, or by accessing more stable water sources in the soil (e.g., by developing deeper roots), or by decoupling from the atmosphere (e.g., stomata control or leaf area loss) Oliveira et al., 2019;Westoby et al., 2002). In this sense, describing the relationship between plant traits and climate is complicated by the fact that plants can adopt different strategies for coping with seasonal water shortage. Nevertheless, this is fundamental to highlight plant responses to future changes in climate, and the results confirm the importance of Ψ tlp as a functional trait for species and ecosystems description, allowing assessment of their comparative drought tolerance and their potential sensitivity to climate change . Boxplots showed variable importance ranked by the RMSE loss after permutations, while solid lines are marginal effects (mean ± 2 SE). BIO1.95, 95th percentiles of average temperature; BIO4, temperature seasonality; CFD.ann, annual consecutive frost days where temperature was ≤0°C; CDD.ann, annual consecutive dry days where precipitation was <1 mm; BIO12.5, 5th percentiles of cumulate annual precipitation; BIO15, precipitation seasonality. Please note that all predictors have been centered and scaled to unit variance. Information related to the other models is available in Figures S3  and S4. Silhouettes were retrieved from http://phylo pic.org. patterns of Ψ tlp in the study area, based on the relationship between current climate and actual distribution of Ψ tlp values. Notably, the direction of Ψ tlp shifts was heterogeneous in the study area. This is highlighted by the different projections emerging in lowlands compared with the Alpine sector. While plant communities at lower elevations will likely undergo a reduction in Ψ tlp , a contrasting signal emerged for the Alpine sector, with an apparent shift toward higher Ψ tlp . These results suggest that climate change will likely have two major effects on plant communities' composition. On one hand, the projected increase in frequency/intensity of drought events in lowlands will endanger drought-sensitive species while favoring more resistant ones. The data presented here (Figure 2c,d) indicate that, particularly among the angiosperms, OGUs characterized by more extreme temperature values also display lower Ψ tlp . Climate change may amplify temperature stress and eventually mortality, particularly if warmer conditions are associated with prolonged droughts F I G U R E 3 Projections of turgor loss point shifts (ΔΨ tlp , %) based on two RCP scenarios (RCP 2.6 and RCP 8.5) computed on model HadGEM2-RACMO22E for (a) gymnosperms, (b) angiosperms, (c) herbaceous angiosperms, and (d) woody angiosperms. Brown tones indicate a shift toward more negative values of Ψ tlp while bluish tones denote a shift toward higher values of Ψ tlp . Silhouettes were retrieved from http:// phylo pic.org. (Fontes et al., 2018), even though the timing of climate change effects can be species-specific (Vanoni et al., 2016). In contrast, the projected increase of temperature and the reduction of frost days in the Alpine sector, where water availability is not a limiting factor, will likely favor the spread of species positioned toward the fast portion of the acquisitive-conservative continuum (Petruzzellis et al., 2021;Rosas et al., 2019), which are characterized by lower drought resistance and carbon cost, but higher photosynthetic and growth rates. This agrees with recent research suggesting that prolonged climatic extremes might promote persistent changes in Alpine plant communities and their associated ecosystem functions (De Boeck et al., 2018). Finally, the interplay of drought and frost events might strongly influence water balance and even carbon metabolism, further increasing species vulnerability to climate change .

| Ecological consequences of projected shifts of Ψ tlp in an accelerated climate change scenario
The sensitivity of species and communities to climate change is strongly influenced by both the intrinsic features of the species (e.g., traits and phylogeny) and the current vegetation type (Fei et al., 2017;Scott et al., 2014). Plants can adjust Ψ tlp in response to fluctuations of soil water availability by accumulating solutes to decrease leaf osmotic potential, or by developing new leaves with higher solute concentrations (Bartlett et al., 2014).
However, Ψ tlp plasticity is overall moderate, with an average possible adjustment of 0.44 MPa (Bartlett et al., 2014). Accordingly, the possible future changes of plant communities' composition in the study area will likely depend on the ability of plant species to adjust their Ψ tlp in response to projected climate changes.

F I G U R E 4
Relative number of species (%) potentially threatened by climate change in the simulated scenarios (high vs. low plasticity) where species were able to adjust their Ψ tlp by 0.44 and 0.22 MPa, respectively. Upper panels represent the high plasticity scenarios for angiosperms (left panels) and gymnosperms (right panels), whereas lower panels represent the lower plasticity scenario. This simulation was performed considering only the high-emission scenario (RCP 8.5).
Based on the simulations, approximately 75% of the species are at risk to exceed the limits of their physiological plasticity in the worst-case scenario that assumes lower species' plasticity. This is in line with recent studies showing that some of the most iconic European forest species, such as Fagus sylvatica and Picea abies, are now historically closest to their drought limits (Leuschner, 2020;van der Maaten-Theunissen et al., 2013). This fact is further corroborated by the steady increase in drought events and associated die-back events that occurred in Europe over the last decades (Senf et al., 2020), which pose serious threats to the health of European forests. As a result, drier conditions can disrupt local adaptations, promoting upslope migrations (Anderson & Wadgymar, 2020) and rearrangements of species pools, favoring ecological strategies based on drought tolerance or avoidance (Wilcox et al., 2021). Species with higher genetic diversity and interspecific trait variability might cope better with the new conditions (i.e., acclimation) (Choat et al., 2018), but data for both intra-and interspecific plasticity of hydraulic traits are still largely absent from the literature (see Tomasella et al., 2018), therefore impeding a finer modelling approach.
Beyond ecological consequences, these changes might also imply modifications of ecosystem services delivered by plant communities. For example, prolonged droughts may increase the occurrence of species that are characterized by harder leaves and more lignified stems, which are usually less digestible by livestock (Lens et al., 2016;Nardini, 2022). Future efforts should focus on monitoring the effects of ongoing global changes on natural vegetation.
In this sense, modelling water relation traits, such as leaf turgor loss point over larger spatial extents, while including more species in these analyses, might strongly improve the capacity to effectively anticipate the effects of climate change.

ACK N OWLED G M ENTS
The study was supported by the University of Trieste (Finanziamenti

CO N FLI C T O F I NTE R E S T
The authors declare no competing interests.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data used in the current study are available in the Zenodo repository: https://doi.org/10.5281/zenodo.6977164.